It is known to continuously deposit grains of a refractory material, for example grains of crystallized quartz, into the base and internal wall of a mold rotating about its vertical axis. When this operation has been carried out, a heat source is introduced into the mold, still kept in rotation, in such a way as to melt the grains to a certain depth. This method enables crucibles of silica, for example, to be produced.
At the same time, in order to economize the quantity of material necessary and reduce the time required for the filling operation, it is desirable to accurately control the means used for introducing the grains of material.
It is already known, from U.S. Pat. No. 4,528,163, to introduce quartz grains by means of a cranked tube, connected at its upper part to a hopper filled with quartz; the opening formed at the lower end of said tube is orientated towards the lateral wall of the mold. A layer of grains is obtained by raising the lower end of the tube from the bottom of the mold to the summit of the lateral wall. The speed of raising is constant and is preregulated as a function of the quantity of material which flows from the tube.